Navigation system

ABSTRACT

A navigation system includes: a storage unit having stored therein roadmap data, first statistical traffic information data pertaining to a first area which are created based upon a first standard related to a time applicable to the first area, and second statistical traffic information data pertaining to a second area which are created based upon a second standard related to a time applicable to the second area; a search unit that searches for a recommended route; and an estimated time of arrival calculation unit that calculates an estimated time of arrival based upon the roadmap data, the first statistical traffic information data and the second statistical traffic information data. The estimated time of arrival calculation unit executes calculation processing of the estimated time of arrival in compliance with the first standard and the second standard.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/892,670, filed Sep. 28, 2010, which claims priority to JapanesePatent Application No. 2009-225204, filed Sep. 29, 2009, and JapanesePatent Application No. 2009-225205, filed Sep. 29, 2009, the entiredisclosures of which are herein expressly incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a navigation system that executes aroute search by using statistical traffic information.

2. Description of Related Art

A navigation system may be capable of executing a route search operationand a required traveling time calculation by taking into considerationtraffic congestion conditions based upon traffic information. However,while the route search operation and the required traveling timecalculation are executed based upon the traffic information available atthe time of the route search operation, the congestion conditions maychange significantly while the vehicle is en route. Japanese Laid OpenPatent Publication No. 2008-96445 discloses a technology whereby trafficinformation collected in the past is accumulated as statistical data,statistical data for individual links are extracted in correspondence tospecific traffic information collection conditions having been selected,changes in the congestion conditions corresponding to various timepoints are superimposed over a map on display and a search for ashortest route is executed with accuracy.

In addition, while the congestion conditions are bound to change as timepasses following the time point at which the traffic information isobtained, an accurate search for a recommended route may be executedbased upon statistical traffic data collected in the past, whichcorrespond to a specific category of day, e.g., a weekday or a holiday,as disclosed in Japanese Laid Open Patent Publication No. 2004-239741.

SUMMARY OF THE INVENTION

Statistical traffic data must be used by taking into considerationtime-related conditions at the start point and the destination that maynot always match, e.g., the start point and the destination may belocated in different time zones or located in areas observing differentholidays. According to the invention disclosed in Japanese Laid OpenPatent Publication No. 2008-96445, the route search is executed at thetime of departure by using statistical traffic data based upon thecurrent time point designated as a departure time point or a departuretime point entered by the user. This means that the route search will beexecuted by using the statistical traffic data based upon the wrong timeif the vehicle is to cross over into a different time zone as it travelsor if the vehicle traveling in an area observing daylight saving time isto move into an area where the daylight saving time is not implemented.

The second conversion table correlating dates with specific daycategories according to the invention disclosed in Japanese Laid OpenPatent Publication No. 2004-239741 remains unchanged unless the userperforms a specific operation. This gives rise to an issue in that theroute search is likely to be executed by using the statistical trafficdata based upon the wrong day category as the vehicle crosses over aborder into a region where different holidays are observed or crossesover a border into another country.

According to the first aspect of the present invention, a navigationsystem comprises: a storage unit having stored therein roadmap dataexpressing a road map between a start point, from which a mobile bodydeparts, and a destination for the mobile body, first statisticaltraffic information data pertaining to a first area where the startpoint is located, which are created based upon a first standard relatedto a time applicable to the first area, and second statistical trafficinformation data pertaining to a second area where the destination islocated, which are created based upon a second standard related to atime applicable to the second area; a search unit that searches, basedupon the roadmap data, for a recommended route for the mobile bodytraveling from the start point to the destination; and an estimated timeof arrival calculation unit that calculates an estimated time of arrivalat which the mobile body, traveling through the recommended route, isexpected to arrive at the destination, based upon the roadmap data, thefirst statistical traffic information data and the second statisticaltraffic information data. The estimated time of arrival calculation unitexecutes calculation processing of the estimated time of arrival basedupon the first statistical traffic information data in compliance withthe first standard and calculates the estimated time of arrival basedupon results of the calculation processing having been executed and thesecond statistical traffic information data in compliance with thesecond standard.

According to the second aspect of the present invention, in thenavigation system according to the first aspect, it is preferred thatthe navigation system further comprises: a clocking unit that clocks ina departure time point at which the mobile body departs the start pointin reference to a start point local standard time in a time zone wherethe start point is located; an estimated passing time point calculationunit that calculates, in reference to the start point local standardtime, a first estimated passing time point, indicating an estimated timepoint at which the mobile body is expected to pass through a waypoint onthe recommended route through calculation of a traveling time lengthexecuted by referencing the first statistical traffic information databased upon the departure time point; and an acquisition unit thatreferences the second statistical traffic information data inconjunction with a second estimated passing time point obtained byconverting the first estimated passing time point to a time point incompliance with destination local standard time in a time zone where thedestination is located when calculating a traveling time length andobtains the estimated time of arrival in the destination local standardtime. The first standard is the start point local standard time; thesecond standard is the destination local standard time; and theestimated time of arrival calculation unit includes the estimatedpassing time point calculation unit and the acquisition unit.

According to the third aspect of the present invention, in thenavigation system according to the first aspect, it is preferred thatthe navigation system further comprises: a clocking unit that clocks ina departure time point at which the mobile body departs the start pointin reference to a start point local standard time in a time zone wherethe start point is located. The first standard is the start point localstandard time; and the second standard is a destination local standardtime in the time zone where the destination is located; and the searchunit searches for the traveling route by searching for a route segmentextending from the start point to a waypoint on the recommended routethrough which the mobile body is to pass, based upon the departure timepoint, the first statistical traffic information data, and the startpoint local standard time, calculating a first estimated passing timepoint at which the mobile body is expected to pass through the waypointand searching for a route segment extending from the waypoint to thedestination based upon a second estimated passing time point obtainedthrough conversion of the first estimated passing time point to a timepoint in compliance with the destination local standard time, the secondstatistical traffic information data and the destination local standardtime.

According to the fourth aspect of the present invention, in thenavigation system according to the first aspect, it is preferred thatthe navigation system further comprises: a clocking unit that clocks ina first departure time point at which the mobile body departs the startpoint in reference to a start point local standard time in a time zonewhere the start point is located; a first time point calculation unitthat calculates a traveling time length by referencing the firststatistical traffic information data and the second statistical trafficinformation data in conjunction with a second departure time pointobtained through conversion of the first departure time point to a timepoint in compliance with a global standard time so as to calculate afirst expected arrival time point indicating a time point at which themobile body is expected to arrive at the destination in the globalstandard time; and a second time point acquisition unit that obtains asecond expected arrival time point calculated by converting the firstexpected arrival time point to a time point in compliance withdestination local standard time in a time zone where the destination islocated. Both the first standard and the second standard are the globalstandard time; the estimated time of arrival calculation unit includesthe first time point calculation unit and the second time pointacquisition unit; and the estimated time of arrival is the secondexpected arrival time point.

According to the fifth aspect of the present invention, in thenavigation system according to the first aspect, it is preferred thatthe navigation system further comprises: a clocking unit that clocks ina first departure time point at which the mobile body departs the startpoint in reference to a start point local standard time in a time zonewhere the start point is located. Both the first standard and the secondstandard are global standard time; and the search unit searches for thetraveling route based upon a second departure time point obtained byconverting the first departure time point to a time point in globalstandard time, the first statistical traffic information data and thesecond statistical traffic information data, and the global standardtime.

According to the sixth aspect of the present invention, in thenavigation system according to the first aspect, it is preferred thatthe navigation system further comprises: a detection unit that detects aposition of the mobile body; a selection unit that selects firstcalendar data corresponding to the first area and second calendar datacorresponding to the second area among sets of calendar data for aplurality of regions; a determining unit that determines a first daycategory corresponding to a traveling date on which the mobile bodytravels through a first road segment present in the first area along therecommended route and a second day category corresponding to a travelingdate on which the mobile body travels through a second road segmentpresent in the second area along the recommended route by referencingthe first calendar data and the second calendar data having beenselected by the selection unit; and an arithmetic operation unit thatcalculates an estimated time of arrival at which the mobile body isexpected to arrive at the destination based upon the first day categoryand the second day category determined by the determining unit, timepoints at which the mobile body is to travel through the first roadsegment and the second road segment, and the first statistical trafficinformation data and the second statistical traffic information data.The start point is the position of the mobile body detected by thedetection unit; the first calendar data related to a calendar observedin the first area and the first day category and the second calendardata related to a calendar observed in the second area and the secondday category are stored in the storage unit; the first standard is thefirst day category; the second standard is the second day category; andthe estimated time of arrival calculation unit includes the arithmeticoperation unit.

According to the seventh aspect of the present invention, in thenavigation system according to the sixth aspect, it is preferred thatthe selection unit identifies a region through which the recommendedroute extends based upon the roadmap data.

According to the eighth aspect of the present invention, in thenavigation system according to the sixth aspect, it is preferred thatthe navigation system further comprises: an interface unit that acceptsan instruction entered by a user to specify the first area and thesecond area.

According to the ninth aspect of the present invention, in thenavigation system according to the first aspect, it is preferred thatthe navigation system further comprises: a detection unit that detects aposition of the mobile body; a selection unit that selects firstcalendar data corresponding to the first area and second calendar datacorresponding to the second area among sets of calendar data for aplurality of regions; and a determining unit that determines a first daycategory corresponding to a traveling date on which the mobile bodytravels through a first road segment present in the first area along therecommended route and a second day category corresponding to a travelingdate on which the mobile body travels through a second road segmentpresent in the second area along the recommended route by referencingthe first calendar data and the second calendar data having beenselected by the selection unit. The start point is the position of themobile body detected by the detection unit; the first calendar datarelated to a calendar observed in the first area and the first daycategory and the second calendar data related to a calendar observed inthe second area and the second day category are stored in the storageunit; the first standard is the first day category; the second standardis the second day category; and the search unit searches for therecommended route based upon the first day category and the second daycategory having been determined by the determining unit, time points atwhich the mobile body is to travel through the first road segment andthe second road segment, and the first statistical traffic informationdata and the second statistical traffic information data.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a configuration of a navigation system that may be adoptedin an embodiment of the present invention.

FIG. 2 illustrates how statistical traffic information stored in theauxiliary storage device may be managed.

FIG. 3 presents a flowchart of the processing executed when calculatingand displaying an estimated time of arrival at the destination via aselected route.

FIG. 4 presents a flowchart of processing executed when calculating anestimated time of arrival at the destination based upon a globalstandard time (Universal Time).

FIG. 5 presents a flowchart of the processing executed when calculatingan estimated time of arrival at the destination based upon localstandard time.

FIG. 6 illustrates a route from a start point to a destination that maybe determined through a search.

FIG. 7 shows the overall configuration of the estimated destinationarrival time calculation system.

FIG. 8 presents a flowchart of processing executed when calculating anddisplaying the estimated time of arrival at the destination by executingroute search operation in conjunction with statistical trafficinformation based upon Universal Time or local standard time.

FIGS. 9A and 9B each present an example of a day category registrationtable that may be stored in the auxiliary storage device.

FIG. 10 presents a flowchart of the processing executed when calculatingan estimated time of arrival at the destination.

FIG. 11 presents a flowchart of processing executed when calculating anddisplaying an estimated time of arrival at the destination by executingroute search operation in conjunction with statistical trafficinformation corresponding to a specific day category.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows the configuration of a navigation system 100 in referenceto which a first embodiment and a second embodiment are to be described.

-First Embodiment-

In reference to FIGS. 1 through 6, the first embodiment of thenavigation system according to the present invention, which is installedin a vehicle, is described. A CPU 110 in FIG. 1 is an arithmeticoperation processing device that controls the entire navigation system100. The CPU 110 and its peripheral devices are connected with oneanother via a bus. The peripheral devices include a main storage device115, an auxiliary storage device 140 and a display module 150. The mainstorage device 115 is constituted with a work memory used as a work areaby the CPU 110 and a program memory where a control program is stored.

Signals originating from a current position detection device 120 and auser input device 130 are input to the CPU 110. The current positiondetection device 120 may be constituted with, for instance, a GPSsensor, a gyro sensor and a vehicle speed sensor. Time point data areincluded in the data input from the GPS sensor, and the CPU 110 has aclock function for correcting the current time point based upon the timepoint data, i.e., the CPU 110 is equipped with an internal clock and acalendar function. The user input device 130 may be constituted with atouch panel, pushbutton switches disposed around the panel, a remotecontrol unit and a joystick.

The auxiliary storage device 140 is a storage device in which roadmapdata and POI (point of interest) information, i.e. information relatedto sightseeing spots and various types of facilities, to be used innavigation processing are stored. The auxiliary storage device 140 maybe a hard disk drive, a CD or DVD in which roadmap data are stored, aflash memory or another type of recording medium, or a reader devicecapable of reading out roadmap data.

Roadmap data provide information related to maps and include map displaydata, route search data and guidance data. The map display data are usedto display roads and backgrounds in a road map. The route search data,which include branch information not directly related to road shapes,are mainly used when calculating through arithmetic operation arecommended route, i.e., when executing a route search. The guidancedata include information indicating intersection names, road names,direction names and landmarks and are used when providing route guidanceto the user based upon the recommended route having been calculated.

A given road in the roadmap data is expressed as link string data withintersections and the like defined as nodes and road segments extendingbetween nodes defined as links. A set of link string data is thusconstituted with node data and link data. Node data and link data,grouped into units of mesh areas each assigned with a specific meshcode, are stored as the roadmap data. The term “mesh area” is used torefer to each of areas assuming a predetermined areal range, into whicha road map is partitioned. In a mesh code storage area, a numberidentifying the corresponding mesh area is stored. In a link string datastorage area, coordinates indicating node positions, link numbersidentifying the links present between nodes and coordinates indicatingthe positions of interpolation points each dividing a link into shortersegments are stored. These positional coordinates are used as contourdata in map display processing and locator processing.

Information indicating the local time corresponding to each mesh areaand information indicating a daylight saving time observation period ineach mesh area are stored together with the roadmap data in theauxiliary storage device 140. Statistical traffic information is alsomanaged in correspondence to individual mesh codes at the auxiliarystorage device 140. The statistical traffic information is to bedescribed in detail in reference to FIG. 2 later. The display module 150brings up a screen display of image data containing text and graphics,which are output from the CPU 110.

FIG. 2 illustrates how the statistical traffic information stored in theauxiliary storage device 140 may be managed. As explained earlier, thestatistical traffic information is managed in units of individual meshcodes. The statistical traffic information corresponding to mesh code#x_(—)1 assumes a hierarchically layered structure and is stored incorrespondence to primary day categories indicating specific day types.There may be five different day categories; “weekday (regular day),weekday (day before holiday)”, “holiday (first day of consecutiveholidays)”, “holiday (middle day of consecutive holidays)” and “holiday(last day of consecutive holidays)”. Since the characteristics oftraffic conditions vary with the day categories, the statistical trafficinformation is managed in correspondence to the individual daycategories.

In the next hierarchical layer after the day category layer, statisticalinformation is stored in correspondence to each of the link numbersindicating the links contained in the mesh area represented by mesh code#x_(—)1. For instance, the statistical traffic information stored incorrespondence to link number #y_(—)1 is organized in correspondence todifferent time frames in the subsequent hierarchical layer. Thestatistical traffic information for a time frame 0:00 through 1:00,among the time frames, indicates a traveling time of 257 seconds andcongestion level 1 in the example presented in FIG. 2. This means thatthe length of time required to travel through the link represented bylink number #y_(—)1 in the mesh area assigned with mesh code #x_(—)1 isestimated to be 257 seconds in the time frame between 0:00 a.m. and 1:00a.m. and that the conditions of traffic congestion experienced by thevehicle are likely to be level 1.

Next, the route search processing executed by using statistical trafficinformation in the navigation system 100 in the embodiment is describedin detail. The processing executed by using timeframe-by-timeframestatistical traffic information, such as that shown in FIG. 2, managedin correspondence to different time frames based upon a global standardtime (Universal Time) and the processing executed by usingtimeframe-by-timeframe statistical traffic information based upon localstandard time are individually explained in reference to FIGS. 3 through6. FIG. 6 presents an example of a route from a start point S to adestination G that may be determined through a search. Mesh areas M10and M20 are adjacent to each other. The searched route is made up withlinks L11, L12 and L21. While the links L11 and L12 are present in themesh area M10, the link L21 is present in the mesh area M20. The linkL11 connects the start point S to a waypoint, the link L12 connects thewaypoint to a waypoint and the link L21 connects the waypoint to thedestination G.

(1) Route Search Execution Processing with Timeframe-by-TimeframeStatistical Traffic Information Based Upon Universal Time.

The navigation system 100 determines the date/time of departure and aspecific day of the week on which the date falls (hereafter “thedate/time and a specific day of the week” is to be referred to as a“time point and the like”) by engaging the clock function of the CPU 110at which the local standard time is set, and then converts the timepoint and the like to time point and the like in Universal Time. Next,the lengths of traveling time likely to be required to travel throughthe links L11, L12 and L21 in Universal Time are read out from thetimeframe-by-timeframe statistical traffic information managed as shownin FIG. 2. The lengths of link traveling time are added to the departuretime point and the like in order to calculate an estimated time ofarrival at the destination in Universal Time, the estimated time ofarrival and the like thus calculated are then converted to an estimatedtime of arrival and the like in local standard time matching the settingat the clock function in the CPU 110 and the estimated time of arrivaland the like in local standard time are brought up on display at thepanel in the display module 150.

It is to be noted that if the mesh areas M10 and M20 are located indifferent time zones, the estimated time of arrival will be converted toan estimated time of arrival at the destination in the local standardtime in the time zone of the destination and the estimated time ofarrival resulting from the conversion will be brought up on display atthe panel in the display module 150. When the vehicle travels throughareas located in different time zones, as described above, theprocessing must be executed by taking into consideration whether or notdaylight saving time is applicable in each area. The time differencebetween the local time at the start point and the local time at thedestination may also be indicated to the user in the form of a messagebrought up in a screen display or a voice message.

(2) Route Search Execution Processing with Timeframe-by-TimeframeStatistical Traffic Information Managed in Correspondence to DifferentTime Frames Based Upon the Local Standard Time.

The navigation system 100 determines the departure time point and thelike by engaging the clock function of the CPU 110 at which the localstandard time is set. Next, the lengths of traveling time likely to berequired to travel through the links L11, L12 and L21 in local standardtime are read out from the timeframe-by-timeframe statistical trafficinformation managed as shown in FIG. 2. The lengths of link travelingtime are added to the departure time point and the like so as tocalculate an estimated time of arrival at the destination and the like,which are then brought up on display at the panel in the display module150.

It is to be noted that if the mesh areas M10 and M20 are located indifferent time zones, the lengths of traveling time likely to berequired to travel through the links present in the mesh area M10 willbe read out and then a time point at which the subject vehicle is likelyto travel through the border between the mesh areas will be determinedby adding the sum of the lengths of link traveling time likely to berequired to travel through the links present within the mesh area M10 tothe departure time point and the like. When the vehicle travels throughareas located in different time zones, as described above, theprocessing must be executed by taking into consideration whether or notdaylight saving time is applicable in each area. The time point at whichthe subject vehicle is expected to travel through the border between themesh areas, initially determined in local time in the time zone of themesh area M10, will be converted to a time point in the local standardtime in the time zone of the mesh area M20, through which the subjectvehicle having driven through the border is to travel, is located. Anestimated time of arrival at the destination in the local standard timein the time zone of the mesh area M20, obtained by reading out thelengths of traveling time likely to be required to travel through thelinks in the mesh area M20 and adding the sum of the link traveling timelengths to the time point at which the subject vehicle is expected tocross the border in the local standard time in the time zone of the mesharea M20, will then be brought up on display at the panel in the displaymodule 150. The time difference between the local time at the startpoint and the local time at the destination may also be indicated to theuser in the form of a message brought up in a screen display or a voicemessage.

FIG. 3 presents a flowchart of the route search arithmetic operationprocessing and the processing for calculating and displaying anestimated time of arrival at the destination through the selected route,executed by the CPU 110 in the navigation system 100.

In step S301, the current position of the vehicle equipped with thenavigation system 100 is detected via the current position detectiondevice 120. In step S302, a decision is made as to whether or notinstructions for setting a destination and executing route searcharithmetic operation, issued by the user via the user input device 130,have been received. Until these execution instructions are received,step S302 is repeatedly executed in this processing procedure. Once theexecution instructions have been received, the route search arithmeticoperation is executed in step S303. In step S304, route search resultsare brought up on display at the display panel of the display module150. In step S305, a decision is made as to whether or not aninstruction for executing route selection, issued by the user via theuser input device 130, has been received. Until this executioninstruction is received, step S305 is repeatedly executed in thisprocessing procedure. Once the execution instruction has been received,an estimated destination arrival time calculation subroutine, to bedetailed later, is executed in step S306. The estimated time of arrivalat the destination, resulting from the subroutine, is brought up ondisplay at the display panel of the display module 150 in step S307, andthen the processing procedure ends.

FIGS. 4 and 5 each present a flowchart of the estimated destinationarrival time calculation subroutine mentioned above. As explainedearlier, the timeframe-by-timeframe statistical traffic information inFIG. 2 may be managed based upon Universal Time or based upon the localstandard time. The estimated destination arrival time calculationprocessing procedure executed based upon timeframe-by-timeframestatistical traffic information managed based upon Universal Time isdescribed in reference to FIG. 4. The estimated destination arrival timecalculation processing procedure executed based upontimeframe-by-timeframe statistical traffic information managed basedupon local standard time is described in reference to FIG. 5.

FIG. 4 shows the procedure for the estimated destination arrival timecalculation processing subroutine executed based upon Universal Time instep S306 in FIG. 3. In step S401, the current date/time, ascertainedvia the clock function of the CPU 110, is converted to a time point Tbased upon Universal Time. In step S402, n mesh areas through which theselected route extends are sorted in the order in which the subjectvehicle, traveling from the start point toward the destination, passesthrough the individual mesh areas (i=1, 2, . . . n). Subsequently, thesequence of processing from step S403 through step S412 and step S413 isrepeatedly executed for all the mesh areas i=1 through n.

In step S403, a time point T′ in local standard time of the time zone ofthe mesh area #i is set based upon latitude/longitude information byreferencing the local standard time information stored in the auxiliarystorage device 140. In step S404, a decision is made as to whether ornot daylight saving time is applicable in the mesh area #i byreferencing daylight saving time information stored in the auxiliarystorage device 140. If an affirmative decision is made, the time pointT′ is adjusted by factoring in daylight saving time in step S405 beforethe processing proceeds to step S406. If, on the other hand, a negativedecision is made, the processing directly proceeds to step S406.

In step S406, the estimated time points T and T′ at which the subjectvehicle is expected to enter the mesh area #i are stored into the mainstorage device 115 or the auxiliary storage device 140. In step S407,the link numbers assigned to the links constituting the selected routeare sorted in the order in which the corresponding links are to betraveled (j=1, 2, . . . m). Subsequently, the sequence of processingfrom step S408 through step S410 and step S411 is repeatedly executedfor all the links j=1 through m.

In step S408, the length of traveling time t_ij likely to be required totravel through the link #j at the time point T is searched byreferencing the statistical traffic information stored in correspondenceto the individual mesh codes in the auxiliary storage device 140. Instep S409, estimated time points T and T′ at which the vehicle isexpected to finish traveling through the link #j, determined based uponthe traveling time t_ij for the link #j, are stored into the mainstorage device 115 or the auxiliary storage device 140.

In step S410, a decision is made as to whether or not j is equal to m(“j=m?”) so as to determine whether or not expected travel end timepoints T and T′ have been calculated for all the links present in themesh area #i. If a negative decision is made, j is incremented to j+1 instep S411 and the processing returns to step S408. However, if anaffirmative decision is made, the processing proceeds to step S412.

In step S412, a decision is made as to whether or not i is equal to n(“i=n?”) so as to determine whether or not expected travel end timepoints T and T′ have been calculated for all the mesh areas throughwhich the selected route extends. If a negative decision is made, i isincremented to i+1 in step S413 and the processing returns to step S403.However, if an affirmative decision is made, the processing proceeds tostep S414. Once the estimated destination arrival time points T and T′have been stored in step S414, the subroutine ends and the processingreturns to the main routine in FIG. 3.

FIG. 5 shows the procedure for the estimated destination arrival timecalculation processing subroutine executed based upon the local standardtime in step S306 in FIG. 3. In step S501, the current date/time,ascertained via the clock function of the CPU 110, is set as a timepoint T in local standard time. In step S502, n mesh areas through whichthe selected route extends are sorted in the order in which the subjectvehicle, traveling from the start point toward the destination, passesthrough the individual mesh areas (i=1, 2, . . . , n). Subsequently, thesequence of processing from step S503 through step S512 and step S513 isrepeatedly executed for all the mesh areas i=1 through n.

In step S503, a time point T in local standard time of the time zone ofthe mesh area #i is set based upon latitude/longitude information byreferencing the local standard time information stored in the auxiliarystorage device 140. In step S504, a decision is made as to whether ornot daylight saving time is applicable in the mesh area #i byreferencing daylight saving time information stored in the auxiliarystorage device 140. If an affirmative decision is made, the time point Tis adjusted by factoring in daylight saving time in step S505 before theprocessing proceeds to step S506. If, on the other hand, a negativedecision is made, the processing directly proceeds to step S506.

In step S506, an estimated time point T at which the subject vehicle isexpected to enter the mesh area #i is stored into the main storagedevice 115 or the auxiliary storage device 140. In step S507, the linknumbers assigned to the links constituting the selected route are sortedin the order in which the corresponding links are to be traveled (j=1,2, . . . , m). Subsequently, the sequence of processing from step S508through step S510 and step S511 is repeatedly executed for all the linksj=1 through m.

In step S508, the length of traveling time t_ij likely to be required totravel through the link #j at the time point T is searched byreferencing the statistical traffic information stored in correspondenceto the individual mesh codes in the auxiliary storage device 140. Instep S509, an estimated time point T at which the vehicle is expected tofinish traveling through the link #j, determined based upon thetraveling time t_ij for the link #j, is stored into the main storagedevice 115 or the auxiliary storage device 140.

In step S510, a decision is made as to whether or not j is equal to m(“j=m?”) so as to determine whether or not expected travel end timepoints T have been calculated for all the links present in the mesh area#i. If a negative decision is made, j is incremented to j+1 in step S511and the processing returns to step S508. However, if an affirmativedecision is made, the processing proceeds to step S512.

In step S512, a decision is made as to whether or not i is equal to n(“i=n?”) so as to determine whether or not expected travel end timepoints T have been calculated for all the mesh areas through which theselected route extends. If a negative decision is made, i is incrementedto i+1 in step S513 and the processing returns to step S503. However, ifan affirmative decision is made, the processing proceeds to step S514.Once the estimated destination arrival time point T has been stored instep S514, the subroutine ends and the processing returns to the mainroutine in FIG. 3.

The navigation system 100 achieved in the first embodiment describedabove is structured so that information indicating the local standardtime in each mesh area and information indicating the period of timeduring which daylight saving time is applicable in each mesh area arestored in advance together with roadmap data. As a result, an advantageis achieved in that even when the subject vehicle is to travel throughdifferent time zones, a route search can be reliably executed by usingstatistical traffic information.

-Variations of the First Embodiment-

The navigation system 100 achieved in the first embodiment as describedabove allows for the following variations.

(1) While the local standard time and the daylight saving schedule areascertained in correspondence to each mesh area in the processing shownin FIGS. 4 and 5, these factors may be considered in correspondence toeach link or each local region instead.

(2) The procedure for the estimated destination arrival time calculationprocessing executed with timeframe-by-timeframe statistical trafficinformation, such as that shown in FIG. 2, managed based upon UniversalTime and the procedure of the estimated destination arrival timecalculation processing executed with timeframe-by-timeframe statisticaltraffic information managed based upon the local standard time have beendescribed in reference to FIGS. 4 and 5 respectively. The operation inthe navigation system may be executed by switching over from one of thetwo types of estimated destination arrival time calculation processingdescribed above to the other. Such a switchover may be triggered by, forinstance, a flag value indicating whether the timeframe-by-timeframestatistical traffic information is currently managed based uponUniversal Time or local standard time or triggered in response to a userinput operation.

(3) While the estimated destination arrival time calculation processingprocedure is executed to determine an estimated time of arrival at thedestination through a route selected based upon the results of a searchbefore the vehicle equipped with the navigation system 100 departs thestart point in the processing shown in FIG. 3, the estimated destinationarrival time calculation processing procedure may also be executed witha given timing after departing the start point so as to indicate theestimated time of arrival at the destination with an even higher levelof accuracy.

(4) In the processing described in reference to FIG. 3, the estimateddestination arrival time calculation processing is executed by usingstatistical traffic information stored in the navigation system 100. Asan alternative, the navigation system 100 installed in a vehicle 10 mayfurther include a communication module 160, statistical trafficinformation may be stored in a server 40 connected to a communicationnetwork 30, and the navigation system 100 may download an estimated timeof arrival at the destination calculated through estimated destinationarrival time calculation processing executed at the server 40, via thecommunication network 30 and an access point 20, as illustrated in FIG.7.

(5) In the processing described in reference to FIG. 3, the navigationsystem 100 executes route search arithmetic operation in step S303 todetermine a route from the current position to the destination. Then, instep S306 the navigation system calculates an estimated time of arrivalat the destination for the route selected in step S305. However, theprocessing may be executed by adopting an alternative method such asthat shown in FIG. 8. FIG. 8 presents a flowchart of the processing forexecuting route search arithmetic operation with statistical trafficinformation based upon Universal Time or the local standard time andcalculating and displaying an estimated time of arrival at thedestination. The processing in this figure differs from that in FIG. 3in that processing steps S803 and S804 are executed in place ofprocessing steps S303, S304 and S307 in FIG. 3. Provided that thetimeframe-by-timeframe statistical traffic information is managed andstored based upon Universal Time, the current time point in localstandard time in the time zone of the start point is first converted toa current time point indicated in Universal Time and then an arithmeticoperation is executed to search for routes between the current positionand the destination by using the timeframe-by-timeframe statisticaltraffic information corresponding to the current time point resultingfrom the conversion in step S803. If, on the other hand, thetimeframe-by-timeframe statistical traffic information is managed andstored based upon local standard time, an arithmetic operation isexecuted to search for routes between the current position and thedestination by using corresponding timeframe-by-timeframe statisticaltraffic information based upon the local standard time in each of themesh areas present between the current position and the destination. Asa result, in addition to various routes extending between the currentposition and the destination, estimated time points of arrival at thedestination through those routes can be determined. Accordingly, in stepS804, the estimated time points of arrival at the destination in localstandard time in the time zone of the destination are displayed,together with the route search results, at the display panel of thedisplay module 150. It is preferable that upon receiving in step S305 aninstruction issued by the user for executing route selection, theprocessing proceed to step S307 to display the estimated time of arrivalat the destination through the selected route at the display panel ofthe display module 150 before ending the estimated destination arrivaltime calculation processing procedure.

(6) While the present invention is adopted in the navigation system 100in the first embodiment and the variations thereof described above, thepresent invention is not limited to this example and it may be adoptedin a PND (personal navigation device), a PDA (personal digitalassistant), a mobile telephone, a portable personal computer or aportable game machine.

-Second Embodiment-

In reference to FIGS. 1 through 3, 6, 9A, 9B and 10, the secondembodiment achieved by installing the navigation system according to thepresent invention in a vehicle is described.

While the navigation system 100 in the embodiment assumes a structureidentical to that of the navigation system in the first embodiment,already described in reference to FIG. 1, calendar data and day categoryregistration tables each correlating calendar dates with day categoriesare also stored in the auxiliary storage device 140 in addition to thestatistical traffic information shown in FIG. 2. The day categoryregistration tables, to be described in detail later in reference toFIGS. 9A and 9B, are each created in correspondence to a specific regionbased upon the calendar data pertaining to the particular region.

FIGS. 9A and 9B each present an example of a date category registrationtable that may be stored in the auxiliary storage device 140. Asdescribed earlier, calendar dates are correlated to specific daycategories in a day category registration table. The table in FIG. 9Aindicates day categories designated to the five days starting on August28 (Thursday) 2008, when September 1 (Monday), 2008 is a holiday. To bemore specific, August 28 (Thursday) 2008, is categorized as “weekday(regular day)”, the 29th (Friday) is categorized as “weekday (day beforeholiday)”, the 30th (Saturday) is categorized as “holiday (first day ofconsecutive holidays)”, the 31st (Sunday) is categorized as “holiday(middle day of consecutive holidays)” and September the 1st (Monday),2008 is categorized as “holiday (last day of consecutive holidays)”.

In a given region in, for instance, the United States of America,holidays set forth by the state government are observed in addition toholidays set forth by the national government. For this reason, whilethe date category registration table for state A may indicate the daycategory designations in FIG. 9A, the day category registration tablefor state B adjacent to state A may indicate August 28 (Thursday) 2008categorized as “weekday (day before holiday)”, the 29th (Friday)categorized as “holiday (first day of consecutive holidays)”, and the30th (Saturday) categorized as “holiday (middle day of consecutiveholidays)” as shown in FIG. 9B.

The route search execution processing executed in the navigation system100 by using statistical traffic information in the embodiment is nowdescribed in detail. It is assumed that the mesh area M10 in FIG. 6 islocated in state A. Accordingly, statistical traffic information is usedby referencing the day category registration table in FIG. 9A. Since themesh area M20 is located in state B, statistical traffic information isused by referencing the day category registration table in FIG. 9B.

As the subject vehicle departs the start point S on, for instance,August 29 (Friday), 2008, the latitudes/longitudes of the start point S,the destination G and the like are determined based upon input signalsprovided from the current position detection device 120. Thus, thenavigation system 100 is able to locate the start point S in the mesharea M10, i.e., state A, by referencing the roadmap data stored in theauxiliary storage device 140. It is likewise able to locate thedestination G in the mesh area M20, i.e., state B. As FIGS. 9A and 9Bindicate, August 29 (Friday), 2008, which falls on a weekday (day beforeholiday) in state A where the start point S is located, is designated asa holiday (first day of consecutive holidays) in state B where thedestination G is located.

The link traveling time lengths for the links L11, L12 and L21 are readout from the timeframe-by-timeframe statistical traffic informationshown in FIG. 2, in correspondence to the specific day categories havingbeen determined as described above. While the link traveling timelengths for the links L11 and L12 correspond to a weekday (day beforeholiday), the link traveling time length for the link L21 corresponds toa holiday (first day of consecutive holidays). The estimated time ofarrival at the destination G is calculated by adding the sum of the linktraveling time lengths to the departure time point and the calculatedestimated time of arrival is brought up on display at the panel of thedisplay module 150.

The CPU 110 of the navigation system 100 executes the route searcharithmetic operation processing and the processing for calculating anddisplaying an estimated time of arrival at the destination through theselected route by following the procedural steps having already beendescribed in reference to the flowchart presented in FIG. 3.

FIG. 10 presents a flowchart of the estimated destination arrival timecalculation processing subroutine executed in step S306 in FIG. 5. Instep S1001, the current date/time, ascertained via the clock function ofthe CPU 110, is set as a time point T. In step S1002, n mesh areasthrough which the selected route extends are sorted in the order inwhich the subject vehicle, traveling from the start point toward thedestination, passes through the individual mesh areas (i=1, 2, . . . ,n). Subsequently, the sequence of processing from step S1003 throughstep S1010 and step S1011 is repeatedly executed for all the mesh areasi=1 through n.

In step S1003, an estimated time point T at which the subject vehicle isexpected to enter the mesh area #i is stored into the main storagedevice 115 or the auxiliary storage device 140. In step S1004, the linknumbers assigned to the links constituting the selected route are sortedin the order in which the corresponding links are to be traveled (j=1,2, . . . , m). Subsequently, the sequence of processing from step S1005through step S1008 and step S1009 is repeatedly executed for all thelinks j=1 through m.

In step S1005, the region where the link #j in the mesh area #i islocated, is identified based upon the roadmap data stored in theauxiliary storage device 140 and a specific day category X designated tothe current date/time is identified by referencing the day categoryregistration table corresponding to the particular region. In stepS1006, the length of traveling time t_ij likely to be required to travelthrough the link #j at the time point T on the day categorized as X issearched by referencing the statistical traffic information stored incorrespondence to the individual mesh codes in the auxiliary storagedevice 140. In step S1007, an estimated time point T at which thevehicle is expected to finish traveling through the link #j, determinedbased upon the traveling time t_ij for the link #j, is stored into themain storage device 115 or the auxiliary storage device 140.

In step S1008, a decision is made as to whether or not j is equal to m(“j=m?”) so as to determine whether or not expected travel end timepoints T have been calculated for all the links present in the mesh area#i. If a negative decision is made, j is incremented to j+1 in stepS1009 and the processing returns to step S1005. However, if anaffirmative decision is made, the processing proceeds to step S1010.

In step S1010, a decision is made as to whether or not i is equal to n(“i=n?”) so as to determine whether or not expected travel end timepoints T have been calculated for all the mesh areas through which theselected route extends. If a negative decision is made, i is incrementedto i+1 in step S1011 and the processing returns to step S1003. However,if an affirmative decision is made, the processing proceeds to stepS1012. Once the estimated destination arrival time point T has beenstored in step S1012, the subroutine ends and the processing returns tothe main routine in FIG. 3.

The navigation system 100 achieved in the second embodiment as describedby is structured so that day category registration tables prepared incorrespondence to individual regions are stored in advance in theauxiliary storage device 140. Thus, statistical traffic informationcorresponding to a specific day category determined by referencing a daycategory registration table selected in correspondence to the regionwhere the selected route determined based upon search results islocated, can be extracted. As a result, even when the subject vehicletravels through a route crossing over from one region to another wheredifferent holidays are observed, the navigation system 100 is able tocalculate an accurate estimated time of arrival at the destination byexecuting a route search with optimal statistical traffic information.

-Variations of the Second Embodiment-

The navigation system 100 achieved in the second embodiment as describedabove allows for the following variations.

(1) While the navigation system 100 in the second embodiment describedabove detects the current position via the current position detectiondevice 120 and automatically selects the day category registration tablecorresponding to the region where the detected current position islocated, a day category registration table may be manually selected andset when executing the route search arithmetic operation, instead. Forinstance, the user may issue an instruction for the CPU 110 for settinga day category registration table via the user input device 130 and theCPU 110, in response to the instruction, may bring up on display acalendar at the panel of the display module 150. In this case, as theuser specifies a target calendar day, selects a corresponding daycategory and confirms the selection, a day category registration tablewill be set and selected. If, on the other hand, a day categoryregistration table can be selected exclusively from the day categoryregistration tables stored in advance in the auxiliary storage device140, the user may enter the name of the region in which the route islocated and the CPU 110 may select the specific day categoryregistration table corresponding to the entered region name by readingit out from the auxiliary storage device 140. Day category registrationtables each corresponding to a plurality of regions sharing a givenholiday calendar may be classified as a type 1 table, a type 2 table, .. . and the like and, in such a case, the user may select a day categoryregistration table by specifying the type number assigned to theparticular day category registration table instead of entering the nameof the region.

(2) The navigation system 100 in the second embodiment described abovedetermines the day category corresponding to the current date/time byreferencing the day category registration table for the region in orderto calculate the link traveling time length based upon statisticaltraffic information retrieved in correspondence to the day category. Asan alternative, the day category corresponding to the current date/timemay be determined by referencing calendar data available incorrespondence to each region.

(3) In the second embodiment described above, day category registrationtables for various regions are created based upon calendar data for theindividual regions and the day category registration tables are thenstored into the auxiliary storage device 140 in advance. As analternative, the navigation system 100 may further include acommunication module and download via the communication module calendardata for various regions from a server connected to a communicationnetwork.

(4) In the processing described in reference to FIG. 3, the navigationsystem 100 executes route search arithmetic operation in step S303 tosearch for routes from the current position to the destination and thencalculates an estimated time of arrival at the destination in step S306for the route selected in step S305. However, the processing may beexecuted by adopting an alternative method such as that shown in FIG.11. FIG. 11 presents a flowchart of the processing for executing a routesearch arithmetic operation with statistical traffic informationcorresponding to a specific day category and calculating and displayingestimated destination arrival time points. The processing in this figurediffers from that in FIG. 3 in that processing steps S1103 and S1104 isexecuted in place of processing steps S303, S304 and S307 in FIG. 3. Instep S1103, day category registration tables corresponding to theregions where the mesh areas present between the current positiondetected via the current position detection device 120 and thedestination are located, are selected from the day category registrationtables stored in the auxiliary storage device 140, day categories aredetermined by referencing the selected day category registration tablesand route search arithmetic operation is executed to search for routesbetween the current position and the destination by usingtimeframe-by-timeframe statistical traffic information corresponding tothe day categories. As a result, in addition to various routes extendingbetween the current position and the destination, estimated time pointsof arrival at the destination through those routes can be determined.Accordingly, in step S1104, the estimated time points of arrival at thedestination are displayed, together with the route search results, atthe display panel of the display module 150. It is desirable that uponreceiving in step S305 an instruction issued by the user for executingroute selection, the processing proceed to step S307 to display theestimated time of arrival at the destination through the selected routeat the display panel of the display module 150 before ending theestimated destination arrival time calculation processing procedure.

(5) While the present invention is adopted in the navigation system 100in the second embodiment and the variations thereof described above, thepresent invention is not limited to this example and it may be adoptedin a PND, a PDA, a mobile telephone, a portable personal computer or aportable game console.

The first and second embodiments and the variations thereof describedabove may be adopted in combination. In addition, as long as functionscharacterizing the present invention are not compromised, the presentinvention is in no way limited to any of the devices structured andconfigured as has been described in reference to the embodiments.

What is claimed is:
 1. A navigation system, comprising: a currentposition detector that detects a current position of a subject vehicle;a storage that stores statistical traffic information including a firstlength of time which is required to travel through a road segment on afirst day category and a second length of time which is required totravel through the road segment on a second day category different fromthe first day category; a route searcher that searches for a recommendedroute from a start point to a destination of the subject vehicle; and anestimated time of arrival calculator that: for a road segmentconstituting the recommended route: if a day category corresponding to atraveling date on which the subject vehicle is expected to travel is thefirst day category, extracts the first length of time as a length oftraveling time which is required to travel through the road segment whenthe subject vehicle travels through the road segment, and, for anotherroad segment constituting the recommended route, if a day categorycorresponding to the traveling date on which the subject vehicle isexpected to travel is the second day category, extracts the secondlength of time as a length of traveling time which is required to travelthrough the another road segment when the subject vehicle travelsthrough the another road segment, and calculates an estimated time ofarrival at which the subject vehicle is expected to arrive at thedestination based on a current time point and a sum of lengths oftraveling times, each of which is the length of traveling time havingbeen respectively extracted for the road segments constituting therecommended route, wherein: the first length of time is based onstatistics of past traffic information on the first day category and thesecond length of time is based on statistics of past traffic informationon the second day category; and the estimated time of arrival calculatoridentifies the day category on which the subject vehicle is expected totravel for each road segment constituting the recommended route.
 2. Anavigation system according to claim 1, wherein: when a road segment notlocated in a first area in which the start point is located but locatedin a second area corresponding to a different day category from thefirst area constitutes the recommended route, the estimated time ofarrival calculator calculates a date and a time on which the subjectvehicle is expected to start traveling the road segment located in thesecond area, and, based on the date and the time calculated, theestimated time of arrival calculator identifies the day categorycorresponding to the road segment located in the second area.
 3. Anavigation system according to claim 2, wherein: the estimated time ofarrival calculator calculates the estimated time of arrival by assuminga date and a time on which the subject vehicle is expected to endtraveling road segments located in the first area as a date and a timeon which the subject vehicle is expected to start traveling roadsegments located in the second area.
 4. A navigation system according toclaim 1, further comprising: a display that displays the estimated timeof arrival.
 5. A navigation system according to claim 2, furthercomprising: a display that displays the estimated time of arrival.
 6. Anavigation system according to claim 3, further comprising: a displaythat displays the estimated time of arrival.
 7. A navigation system,comprising: a current position detector that detects a current positionof a subject vehicle; a storage that stores statistical trafficinformation including a first length of time which is required to travelthrough a road segment on a first day category and a second length oftime which is required to travel through the road segment on a secondday category different from the first day category; and a route searcherthat: for a road segment: if a day category corresponding to a travelingdate on which the subject vehicle is expected to travel is the first daycategory, extracts the first length of time as a length of travelingtime which is required to travel through the road segment when thesubject vehicle travels through the road segment, and, for another roadsegment constituting the recommended route, if a day categorycorresponding to the traveling date on which the subject vehicle isexpected to travel is the second day category, extracts the secondlength of time as a length of traveling time which is required to travelthrough the another road segment when the subject vehicle travelsthrough the another road segment, and searches for a recommended routefrom a start point to a destination of the subject vehicle based on asum of lengths of traveling times, each of which is the length oftraveling time having been respectively extracted for the road segments,wherein: the first length of time is based on statistics of past trafficinformation on the first day category and the second length of time isbased on statistics of past traffic information on the second daycategory; and the route searcher identifies the day category on whichthe subject vehicle is expected to travel for each road segmentconstituting the recommended route.
 8. A navigation system according toclaim 7, wherein: the route searcher calculates a date and a time onwhich the subject vehicle is expected to start traveling a road segmentnot located in a first area in which the start point is located butlocated in a second area corresponding to a different day category fromthe first area, and, based on the date and the time calculated, theroute searcher identifies the day category corresponding to the roadsegment located in the second area.
 9. A navigation system according toclaim 7 further comprising: a display that displays an estimated time ofarrival at which the subject vehicle is expected to arrive at thedestination.
 10. A navigation system according to claim 8, furthercomprising: a display that displays an estimated time of arrival atwhich the subject vehicle is expected to arrive at the destination. 11.A route search method, comprising: detecting, by a current positiondetector, a current position of a subject vehicle; searching, by a routesearcher, for a recommended route from a start point to a destination ofthe subject vehicle; identifying, by an estimated time of arrivalcalculator, a day category on which the subject vehicle is expected totravel, for each road segment constituting the recommended route; for aroad segment constituting the recommended route: extracting, by theestimated time of arrival calculator, by referencing statistical trafficinformation in a storage, a first length of time which is required totravel through the road segment on a first day category based onstatistics of past traffic information on the first day category as alength of traveling time which is required to travel through the roadsegment when the subject vehicle travels through the road segment if aday category corresponding to a traveling date on which the subjectvehicle is expected to travel is the first day category, and, foranother road segment constituting the recommended route, extracting, bythe estimated time of arrival calculator, by referencing the statisticaltraffic information in the storage, a second length of time which isrequired to travel through the another road segment on a second daycategory based on statistics of past traffic information on the secondday category as a length of traveling time which is required to travelthrough the another road segment when the subject vehicle travelsthrough the another road segment if a day category corresponding to thetraveling date on which the subject vehicle is expected to travel is thesecond day category; and calculating by the estimated time of arrivalcalculator, an estimated time of arrival at which the subject vehicle isexpected to arrive at the destination based on a current time point anda sum of lengths of traveling times, each of which is the length oftraveling time having been respectively extracted for the road segmentsconstituting the recommended route.
 12. A route search method accordingto claim 11, wherein: when a road segment not located in a first area inwhich the start point is located but located in a second areacorresponding to a different day category from the first areaconstitutes the recommended route, a date and a time on which thesubject vehicle is expected to start traveling the road segment locatedin the second area are calculated, and, based on the date and the timecalculated, the day category corresponding to the road segment locatedin the second area is identified.
 13. A route search method according toclaim 12, wherein: the estimated time of arrival is calculated byassuming a date and a time on which the subject vehicle is expected toend traveling road segments located in the first area as a date and atime on which the subject vehicle is expected to start traveling roadsegments located in the second area.
 14. A route search method accordingto claim 11, further comprising: displaying the estimated time ofarrival on a display.
 15. A route search method according to claim 12,further comprising: displaying the estimated time of arrival on adisplay.
 16. A route search method according to claim 13, furthercomprising: displaying the estimated time of arrival on a display.
 17. Aroute search method, comprising: detecting, by a current positiondetector, a current position of a subject vehicle; identifying, by anestimated time of arrival calculator, a day category on which thesubject vehicle is expected to travel, for each of a plurality of roadsegments; for a road segment: extracting, by the estimated time ofarrival calculator, by referencing statistical traffic information in astorage, a first length of time which is required to travel through theroad segment on a first day category based on statistics of past trafficinformation on the first day category as a length of traveling timewhich is required to travel through the road segment when the subjectvehicle travels through the road segment if a day category correspondingto a traveling date on which the subject vehicle is expected to travelis the first day category, and, for another road segment constitutingthe recommended route, extracting, by the estimated time of arrivalcalculator, by referencing the statistical traffic information in thestorage, a second length of time which is required to travel through theanother road segment on a second day category based on statistics ofpast traffic information on the second day category as a length oftraveling time which is required to travel through the another roadsegment when the subject vehicle travels through the another roadsegment if a day category corresponding to the traveling date on whichthe subject vehicle is expected to travel is the second day category;and searching by a route searcher, for a recommended route from a startpoint to a destination of the subject vehicle based on a sum of lengthsof traveling times, each of which is the length of traveling time havingbeen respectively extracted for the road segments.
 18. A route searchmethod according to claim 17, wherein: a date and a time on which thesubject vehicle is expected to start traveling a road segment notlocated in a first area in which the start point is located but locatedin a second area corresponding to a different day category from thefirst area are calculated, and, based on the date and the timecalculated, the day category corresponding to the road segment locatedin the second area is identified.
 19. A route search method according toclaim 17, further comprising: displaying, on a display, an estimatedtime of arrival at which the subject vehicle is expected to arrive atthe destination.
 20. A route search method according to claim 18,further comprising: displaying, on a display, an estimated time ofarrival at which the subject vehicle is expected to arrive at thedestination.